In a mid-November news conference, Chicago Mayor Rahm Emanuel joined other big-city mayors who are insisting they will continue leading “sanctuary cities” in response to President-elect Donald Trump’s hardline positions on illegal immigration. Standing beside immigration activists, area business leaders, and state and federal lawmakers, Emanuel sought to reduce the fear of immigrants living in this country without authorization.

“To all those who are, after Tuesday’s election, very nervous and filled with anxiety . . . you are safe in Chicago, you are secure in Chicago and you are supported in Chicago,” Emanuel announced. “Chicago has in the past been a sanctuary city . . . It always will be a sanctuary city.” Emanuel’s comments came right after Trump’s post-election appearance on CBS’s 60 Minutes, in which the president-elect promised to deport all immigrants with criminal records.

Trump did not explicitly mention sanctuary cities—which are loosely defined as jurisdictions that, as a matter of policy, do not performing routine immigration checks or cooperate with federal immigration authorities. But his “First 100 Days” plan includes cutting off all federal funding to them.

As he told supporters at an August campaign rally in Phoenix, “We block the funding. No more funding. Cities that refuse to cooperate with federal authorities will not receive taxpayer dollars.”

What cities stand to lose

It is estimated that more than 200 cities, including New York City, Chicago, Tucson, and Los Angeles, have publicly stated they will not provide full cooperation to Immigration and Customs Enforcement (ICE) agents. The battle lines sharpened after Trump announced his nomination of Sen. Jeff Sessions of Alabama, for attorney general, widely considered to be an immigration hardliner.

New York alone stands to lose some $10 billion if Trump follows through on his pledge. The city of Boston city risks losing $6 million in federal funding because officials have vowed to welcome all immigrants, regardless of their legal status.

On the West Coast, Los Angeles, which in 1979 became the first city to specifically bar police officers from stopping people to ask about their immigration status, could lose as much as $500 million of its $9 billion budget — including funding for antiterrorism programs and community health centers. The city of San Francisco currently receives nearly $1 billion in federal funds, channeled to everything from Medicare to the Municipal Transportation Agency to homelessness- and crime-reduction projects.

The case against sanctuary cities

Trump isn’t the first conservative critic of sanctuary cities. For years, Republican politicians and advocates for tighter immigration laws have claimed that a lack of cooperation between local law enforcement and federal immigration officials makes sanctuary cities less safe because it results in the release of dangerous individuals who should be deported. Nonetheless, courts already have blocked laws requiring police officers to verify the immigration status of the people they arrest or question.

For instance, an Arizona law required police officers to determine someone’s immigration status if the officer had a “reasonable suspicion” that the person was in the country illegally. Though the U.S. Supreme Court largely upheld the law when it was challenged, earlier this year the state’s attorney general rolled back parts of it and outlined limits on enforcement of immigration laws by police as part of a settlement of a separate lawsuit brought by immigrants’ rights groups.

The architect of the Arizona law? Kansas Secretary of State Kris Kobach, who is now on Trump’s transition team.

Federal funds and police organizations

Some police groups, notably the National Association of Police Organizations, a major lobbying force for law enforcement, have voiced agreement with Trump’s opposition to sanctuary policies. But even NAPO opposes the unilateral cutting of federal purse strings.

“While NAPO supports efforts in Congress to eliminate sanctuary jurisdictions, which pose real threats to the American people, we do not believe that law enforcement should be punished for the decisions of elected officials,” the organization said in a released statement.

ICE and local law enforcement

The legal landscape is shifting when it comes to expectations that local jails should comply with US Customs and Immigration Enforcement “detainers”; i.e., requests to hold noncitizen inmates for an additional 48 hours to face federal custody. In September, a federal judge in Illinois ruled that ICE’s use of detainers to hold inmates without a warrant exceeds the agency’s legal authority.

Local law enforcement officials are also critics of anti-sanctuary city legislation, contending that enforcing immigration laws is problematic not just because they’d be doing the federal government’s work, but because it also undermines their relationships with the communities they protect.

The argument is rooted in the possibility that witnesses or victims of crimes are reluctant to come forward or work with police out of a fear of deportation — a double-bind leading to less safe communities for both immigrants and native-born residents, they argue.

As Los Angeles Police Chief Charlie Beck said in a recent press conference, “Local policing needs the cooperation of the majority of the folks who live within their jurisdiction. Over 500,000 Angelenos, people who live in Los Angeles, are undocumented immigrants. I need their cooperation. I need them to work with their local police stations. I need them to be witnesses to violent crimes. I need them to be the heart of the fabric of Los Angeles if we’re going to keep this city safe.”

About Tracy Collins Ortlieb

Tracy Collins Ortlieb is a digital marketing writer and editor and former daily news journalist who loves the art of crafting a compelling story. She lives in Chicago with her family, two cats and an exhausted library card. You can find her blogging at http://houseofclams.com/ and tweeting at @tracyortlieb.